Process of preventing corrosion



Patented May 28, 1935 PATENT OFFICE raoonss or PREVENTING 'ooaaosIoNHyym E. Buc, Roselle, N. J., assignor to Standard Oil DevelopmentCompany, a corporation of Delaware No Drawing.

Application July 23, 1932,

Serial No. 624,361

Claims.

This invention relates to a process for pre-'- venting corrosion ofmetals in contact with acid alkaline or neutral aqueous mediums and willbe fully understood from the following description:

Two beakers of dilute acetic acid are taken and a piece of copper wireplaced in each. .To one of the beakers a small amount of tertiaryamylphenol is added. -After letting the beakers stand several weeksexposed to the air the solution containing no amyl phenol turns bluewhile the other remains water white. In this case the tertiary amylphenol evidently prevents the acid corrosion of the copper wire.

Extending the scope of this preliminary experiment I have found that thecorrosion of other metals in acid alkaline or neutral aqueous mediumscan be prevented or considerably decreased by the addition of smallamounts of corrosion preventatives of the phenol type and belonginggenerally to the class of substances consisting of phenols, naphthols,alkylated phenols, alkylated naphthols, and the sulfonated derivativesof these various phenolic compounds.

The expression phenol is meant to comprise both mono and polyhydricphenols. Phenolic substances containing other groups besides thehydroxyl such as, for example, amino phenols, may also be used althoughthe phenols and alkylated phenols containing no such additional group inthe ring are preferred.

The expression aqueous medium is to be taken in a broad sense so as tocover cases when the water is present in solution or even only intraces, for example, it is usual to spray coal with calcium chloridesolution to prevent dust formation. In this case the aqueous medium isonly present in traces forming a film over the surface of the coalparticles, yet a serious corrosion of the equipment handling suchtreated coal has been observed. Such corrosion is considerably reducedby the addition of my corrosion preventative substances to the calciumchloride solution before the spraying.

The corrosion of metals may be due to several causes. The main types ofcorrosion known are the oxidation corrosion and the electrolyticcorrosion. I have found that the inhibitors belonging to the abovedescribed class of substances are active with the various types ofcorrosions although they are mostfrequently used with the oxidationtype. When sulfonated derivatives are employed the same are mostconveniently introduced in the form of neutral salts. Alkaline solutionsare generally preferred for the non-sulfonated phenols and naphthols,alkylated phenols and alkylated naphthols, particularly to prevent metalcorrosion due to oxidation.

The following experimental technique was developed for testing theefllciency of the corrosion inhibitors: weighed strips of differentmetals, the 5 surface ofwhich has been measured were left in contactwith the aqueous medium for seven days at a temperature of 160 F. Themetal strips were then taken out, washed, dried and weighed and theirloss or gain of weight was calculated as corrosion over their totalsurface expressed in fractions of an inch of penetration per year. Aloss of weight was designated as positive penetration while a gain ofweight as negative penetration. It will be readily understood that both3 positive and negative penetration are due to corrosion. Positivepenetration is shown, for example, by copper, while aluminum suffersnegative penetration, that is, gain of weight. In the absence ofcorrosion there is, of course, no change in the weight of the'metalstrip. The corrosion in the presence of the corrosion inhibitor was thencompared with the corrosion in the blank runs.

The corrosion in various mediums was studied by the above describedmethod. The following examples will illustrate the action of mycorrosion inhibitors:

0.5% of slightly alkaline solution of tertiary butyl phenol reduces acorrosion in a 29% calcium chloride solution by the following amounts:

Percent 50 50 All these metals sufier positive penetration. Thecorrosion of tin and aluminum by calcium chloride solutions of the samestrength is reduced by by the addition of sodium tertiary butylsulfonate; hydroquinone is somewhat less active. Alpha naphthol wasfound to efficiently reduce the corrosion of steel in 50% solutions oftriethanolamine.

Glycerin solutions containing water, alcohol and castor oil are used forcertain technical purposes, such as for example, radiator solutions forthe cooling systems of internal combustion engines. The use of mycorrosion inhibitors resulted in a reduction of 60 to of the corrosioncaused by such solutions on brass and solder. 1

Several of the solutions described, such as the calcium chloridesolution and the glycerine solution referred to, are commonly classedtogether as anti-freeze solutions.

My corrosion inhibitors may be used in combination with other types ofcorrosion inhibitors with very good results. Thus, for example, thecorrosion of iron is greatly decreased in the presence of small amountsof a mixture of urea and phenol dissolved in the aqueous medium.

The amount of the corrosion inhibitor may vary within considerablelimits. Usually 0.1-0.5% of an inhibitor calculated on the amount of theneutral acid or alkali aqueous medium is sumcient for good results.Sometimes smaller amounts will do and sometimes larger amounts have tobeused. In general the amount of the inhibitor-used is seldom outside thelimits of The inhibitors have to be brought in solution in the aqueousmedium, which is usually easily achieved. The phenolic inhibitor may, ifnecessary, be first dissolved in a small amount of alkali solution andthen added to the aqueous medium.

The invention is not to be limited by any theory nor by the examplesgiven by way of illustration out only by the appended claims in which itis my intention to claim all novelty inherent in the invention.

I. claim:

1. The process of decreasing the corrosion of a metal in contact with anaqueous medium which comprises adding to the medium a small amount of analkylated phenol as corrosion inhibitor.

2. The process of decreasing the corrosion of a metal in contact in anaqueous medium which comprises addingto the medium a small amount of analkylated aromatic compound of the group consisting of alkylated phenolsand alkylated naphthols.

3. The process according to claim 2 in which alkylated phenols are used.

4. The process according to claim 2 in which alkylated naphthol is used.

5. The process according to claim 1 in which the corrosion inhibitor isadded in an amount of 0.02-l%.

6. The process of decreasing the corrosion of radiator solutions usedfor the cooling systems of internal combustion engines, which comprisesadding to such solutions a small amount of an alkylated phenol ascorrosion inhibitor.

7. The process of decreasing the corrosive action of aqueous anti-freezesolutions, which comprises adding thereto from 0.2 to 1% of an alkylatedphenol.

8. The process of decreasing the corrosion of metals in contact with anaqueous medium, which comprises dissolving an alkylated phenol in asmall amount of alkali solution and adding said solution to said aqueousmedium.

9. An anti-freeze composition comprising a water-soluble anti-freezecompound and a small amount of an alkylated phenol.

10. An anti-freeze composition comprising a water-soluble anti-freezecompound and a small amount of an alkylated naphthol.

HYYM E. BUC.

